//建立链表
const a = {val: 'a'};
const b = {val: 'b'};
const c = {val: 'c'};
const d = {val: 'd'};

a.next = b;
b.next = c;
c.next = d;


//插入
const e = {val: 'e'};
c.next = e;
e.next = d;


//删除链表项
c.next = d;


//遍历链表项
let p = a;
while (p){
  console.log(p.val);
  p = p.next;
}
